Question

in how many grams of watwr 36.5 gram HCl should be dissolved so that 10% w/w solution will be obtained

Answer 1

For a 10% w/w solution you need 10 g HCl dissolved in 90 g water.Thus for 36.5 g HCl you will need 36.5*90/10 = 328.50 g of water

Answer 2

w/w% = (mass of solute / mass of solution) × 100
10 = (36.5 / M) × 100
M = 365 g

Mass of water = 365 - 36.5 = 328.5 g

Mass of water should be 328.5 grams.